It's easy to become a superhero. First, discover a superpower. It might take a while to get used to, though---especially if it's something as weird as being your twin brother half the time.
Second, recruit a sidekick. Or, two. It'd be nice if they weren't a pyromaniacal sycophant and a foul-mouthed midget, but you get what you get.
Third, and most important, hire a mentor---preferably not a vicious mobster with a God complex, however, this may, realistically, be your only choice.
go forth and fight crime. Try not to get shot, beaten, tortured, or apprehended in the process.
Good luck!
And, if you find yourself breaking all of the rules mentioned above, well, then you're our hapless hero, Dimorph.